EDWARD A. W. MAUNDER, JOSÉ P.B. MOITINHO DE ALMEIDA AND ORLANDO J.B. ALMEIDA PEREIRA
This paper is concerned
with establishing the nature of the kinematic instabilities that arise in
tetrahedral hybrid equilibrium models when the elements are formulated with
polynomial approximation functions of a general degree. The instabilities are
due to the spurious kinematic (or zero energy) modes, and these modes are first
derived for a single element. The paper continues by identifying those spurious
modes that can be propagated from one element to another via an interface. It
is shown that normally at least three such modes exist for all degrees.
Key words: Equilibrium
models, tetrahedral elements, kinematic stability.